Recently radiolabeled dihydropyridines (DHP's) such as 3H-nitrendipine have been used to identify voltage sensitive calcium channels (VSCC) in many tissues including the brain. Howver, to date VSCC in the brain have been found to be insensitive to such drugs. Thus, the function of the brain DHP receptor is in question at this time. We have identified several neuronal cell lines that do possess VSCC that are blocked by DHP's. We have utilized these cells to identify novel DHP's and toxins (e.g., maitotoxin) that activate VSCC. We propose to examine the properties of VSCC in primary cultures of authentic neurones from the central and peripheral nervous systems. In order to do this, we have devised a specialized microspectrofluorometer capable of analyzing fluorescent signals from single neurones. When cultured neurones such as dorsal root ganglia cells are loaded with the Ca+2 chelating dye, quin-2 they emit a signal which is proportional to the intracellular free [Ca+2]. Thus, on stimulation of the neurone, the influx of Ca+2 via VSCC can be detected as a fluorescent signal. Using this system, we shall analyze the interaction of drugs with VSCC in authentic neurones. In addition, we shall analyze the ability of opiates to mobilize [Ca+2]in in certain neurones.